Replastering Specification
Replastering subsequent to our Chemical Damp Proof Course (DPC) installation is an integral part of our damp proofing system. The importance of compliance with this replastering specification can not be stressed enough. Water rising from the ground contains mineral salts (chlorides, nitrates, sulphates, etc.); these mineral salts are hygroscopic and can attract moisture from the atmosphere. The installation of any chemical DPC alone is unlikely to control the effects of rising damp or the salt contamination of the existing wall plasters, for this reason we always recommend the treated walls be replastered to the following specification:-
- Remove all traces of the existing wall plaster to the specified area.
- Remove embedded timber fixing grounds and make good voids.
- Apply render coat(s) each to a thickness between 8 to 14mm to provide a minimum coverage of approximately 18mm to walls, comprising of:-
- 3 Parts washed sharp sand (BS 1199 Table 1 Grade A or BS882 Table 5 Grade M) to 1 Part cement (Fresh free flowing OPC BS12 or sulphate resisting cement BS4027) using a salt retardant/waterproofing additive in the gauging water to the manufacturers quantities, these components must be throughly mixed together.
- Additional render coats to "dub out" (extra thickness) should be to the same specification and applied before the previous coat has finally set.
- Apply finish plaster (multi-finish) to a nominal thickness of 3mm.
- A gap should be left between solid type floors and the render coats/finish plasters.
The refitting of the original or new skirting boards (primed) should be delayed until the walls have dried sufficiently and has NOT been allowed for within our quotations unless otherwise stated.
Decoration should be delayed (usually two to four weeks) to allow the initial moisture to dry out at that time we recommend that only trade or contract emulsion paints be used. Final decoration should be carried out only when the wall has fully dried out this may take six to twelve months. Even then we do not recommend the use of vinyl paints or papers or other impermeable coatings and decorations which may act as a vapour barrier and prevent the walls from breathing and drying out fully.
DO NOT USE GYPSUM BASED PLASTERS INCLUDING CARLITE & BROWNING. NOT EVEN FOR FIXING ANGLE BEADS, MAKING GOOD, OR DUBBING OUT.
Hacking off wall plaster produces a large amount of dust, and replastering being a wet trade some spillage and droppings often occurs despite our best endeavours. It is important that adequate protection is in place prior to our arrival. It may be necessary for additional cleaning to be carried out following our works, not just to the areas of our works but to others areas within the property. This additional cleaning has not been allowed for within our contract.